This invention relates to rolling bearings in general, and particularly a rolling bearing for supporting a rotary shaft that rotates at a high speed under small radial loads.
As disclosed in JP patent publication 2004-116729, in a rolling bearing for supporting a rotary shaft that rotates at a high speed under small radial loads, such as a main shaft of a jet engine or a spindle of a gas turbine for various industrial machines, its rolling elements, which are retained between the inner and outer rings by a retainer, tend to skid, instead of roll, on the raceways of the inner and outer rings. Excessive skidding of the rolling elements may result in surface damage called smearing on the raceways of the inner and outer rings or the rolling surfaces of the rolling elements. Smearing may develop into surface peeling of the raceways or rolling surfaces, which may in turn cause vibrations or seizure, thus significantly impairing the function of the bearing.
Because smearing and surface peeling resulting from skidding of the rolling elements severely impair the function of the bearing, it is desired to detect the degree of skidding during operation of the bearing as quickly as possible. It is especially acutely desired to detect such skidding in bearings supporting main shafts of jet engines because extremely high level of safety is required for jet engines.
Typically, a jet engine is provided with a sensor for detecting metallic debris in lubricating oil including lubricating oil for bearings. Thus, if surface peeling occurs, the sensor detects debris peeled off bearing parts, thus detecting the surface peeling itself, so that it is possible to inform the pilot of this fact. But it is desired to detect possible smearing and surface peeling beforehand, i.e. before such smearing or surface peeling actually occurs.
An object of the present invention is to provide a rolling bearing including means for detecting skidding of the rolling elements at an earlier stage.